1. Field of the Invention
The present invention relates to a water-insoluble nigrosine compound, a crystalline resin composition and fiber-reinforced crystalline resin molded product both containing said nigrosine compound, a method for lowering the crystallization temperature of a crystalline resin, a method for improving the to fluidity of a crystalline resin, and a method for improving the surface gloss of a crystalline resin.
2. Description of the Prior Art
Being excellent in mechanical and chemical properties, crystalline resins are widely used for molded plastic products in the field of parts of automobiles, electric and electronic products, etc, and their demand is increasing in the field of engineering plastics.
Crystalline resins are colored for decoration, color identification, improvement of light fastness of molded products, content protection and shading and for other purposes. Traditionally, various inorganic pigments and organic dyes/pigments, such as carbon black, black metal complex dyes, azine dyes and perinone black, have been used for black coloring of crystalline resins.
More specifically, examples of colored crystalline resins include a molding formula comprising a polyamide resin colored with carbon black and nigrosine (Japanese Patent Examined Publication No. 43379/1985); a molding composition comprising a polyamide resin colored with carbon black and a copper phthalocyanine pigment (Japanese Patent Unexamined Publication No. 226551/1985); a molding composition comprising an unsaturated polyester resin colored with aniline black and solvent blue (Japanese Patent Examined Publication No. 46524/1989); a plastic molding composition comprising a thermoplastic resin added with carbon black and titanium oxide (Japanese Patent Unexamined Publication No. 186633/1993); a colored resin composition comprising a thermoplastic resin colored with a red organic pigment, a blue organic pigment and a yellow organic pigment (Japanese Patent Unexamined Publication No. 230278/1993); and a mixed resin of polyethylene terephthalate resin and polybutylene terephthalate resin with carbon black dispersed therein (Japanese Patent Unexamined Publication No. 194825/1993).
However, these conventional colored crystalline resin compositions do not always have good appearance and surface gloss, remaining to require further investigation.
In addition, there have been attempts to improve the heat resistance and chemical resistance of crystalline resins or to confer mechanical characteristics suited for various uses, by formulating a fibrous reinforcing material therein, to meet the requirements of a wide variety of industrial applications. Furthermore, in recent years, there has been a marked trend toward replacement of conventional metal parts of products with fiber-reinforced crystalline resin parts, for the purpose of weight reduction, manufacturing process simplification and corrosion prevention, taking note of the good properties of fiber-reinforced crystalline resins as molding materials.
Examples of such fiber-reinforced colored crystalline resins include the polyamide vehicle element described in Japanese Patent Unexamined Publication No. 246958/1987, which comprises a nylon 66/6 copolymer, glass fiber, an inorganic mineral powder and an azine dye; a polyester resin composition for molding comprising a polybutylene terephthalate having a specific viscosity of not less than 0.35, a reinforcing material and carbon black (Japanese Patent Unexamined Publication No. 117951/1990); a thermoplastic resin composition comprising a thermoplastic resin, a modified polyolefin, a fibrous reinforcing material and carbon black (Japanese Patent Unexamined Publication No. 50263/1991); a glass fiber-reinforced black polyamide resin composition comprising a polyamide resin, surface-treated glass fiber and an azine dye (Japanese Patent Unexamined Publication No. 128479/1994); and a polybutylene terephthalate resin composition reinforced with antistatic fiber comprising a glass fiber-reinforced polybutylene terephthalate resin having a volume specific resistivity of not more than 1xc3x971010 xcexa9xc2x7 cm and carbon black (Japanese Patent Unexamined Publication No. 53610/1996).
However, in coloring a fiber-reinforced crystalline resin, there arises the problem of difficulty in thoroughly and uniformly dispersing a coloring agent (e.g., black pigment) in the resin even by kneading for a long time, because of the presence of a fibrous reinforcing material in the resin. In addition, adding a coloring agent can deteriorate the physical properties in comparison with the original resin before its addition, can considerably reduce the fluidity during molding, and can intensify the warpage deformation of the molded product due to a temperature change during molding. In particular, the flotation of the fibrous reinforcing material on the surface of the molded product poses the problem of deterioration of the gloss, appearance, etc. of the colored molded product.
The present invention was developed in view of the above problems in the prior art. Accordingly, the object of the invention is to provide a nigrosine compound which is capable of vividly coloring a crystalline resin (fiber-reinforced or not), which shows particularly good fluidity during molding of a colored crystalline resin, which is excellent in molding precision for the colored crystalline resin, and which favorably improves the appearance-related properties, such as surface gloss, and surface shape or texture, of the molded product, a crystalline resin composition and fiber-reinforced crystalline resin molded product containing said nigrosine compound, a method for lowering the crystallization temperature of a crystalline resin, a method for improving the fluidity of a crystalline resin, and a method for improving the surface gloss of a crystalline resin.
(1) The nigrosine compound of the present invention for accomplishing the above object is a water-insoluble nigrosine compound which is a salt of nigrosine with sulfuric acid and/or phosphoric acid.
The term xe2x80x9csalt of nigrosine with sulfuric acid and/or phosphoric acidxe2x80x9d as used herein refers to a salt of nigrosine (generally hydrochloride) wherein sulfate ions and/or phosphate ions are bound to all or a considerable portion (e.g., not less than 50%, or not less than 70%, and preferably not less than 90%) of the groups capable of binding sulfate ions or phosphate ions. (1-1) The nigrosine compound of Term (1) desirably has a chlorine concentration (i.e., chlorine concentration in nigrosine compound) of not more than 3% by weight.
(1-2) In addition, the nigrosine compound of Term (1) or (1-1) desirably has an iron concentration (i.e., iron concentration in nigrosine compound) of not more than 0.5% by weight.
5 (1-3) In addition, the nigrosine compound of Term (1), (1-1) or (1-2) desirably has a residual aniline concentration (i.e., residual aniline concentration in nigrosine compound) of not more than 0.5% by weight.
(1-4) In addition, the nigrosine compound of Term (1), (1-1), (1-2) or (1-3) desirably has a volume resistivity value of not less than 2.0xc3x971010 xcexa9xc2x7 cm.
(1-5) The nigrosine compound of Term (1), (1-1), (1-2), (1-3) or (1-4) can, for example, be produced by treating nigrosine (generally hydrochloride) with sulfuric acid and/or phosphoric acid. When the nigrosine is a hydrochloride, the treatment of the nigrosine with sulfuric acid and/or phosphoric acid may be such that the chlorine ion constituting the salt in the nigrosine is exchanged with a sulfate ion and/or phosphate ion.
(1-6) Furthermore, the nigrosine compound of Term (1), (1-1), (1-2), (1-3) or (1-4) is desirably a sulfate of nigrosine having a chlorine concentration of not more than 9000 ppm.
20 (2) The crystalline resin composition of the present invention is characterized in that the nigrosine compound of Term (1), (1-1), (1-2), (1-3), (1-4), (1-5) or (1-6) is contained in a crystalline resin.
(2-1) The crystalline resin in the crystalline resin composition of Term (2) is preferably polyamide resin, polyethylene terephthalate resin, polybutylene terephthalate resin or polyphenylene sulfide resin.
(2-2) The crystalline resin composition of Term (2) or (2-1) may have a crystallization temperature lower by not less than 70C than that of the original thermoplastic resin containing no nigrosine compound.
(2-3) The crystalline resin composition of Term (2), (2-1) or (2-2) may contain a fibrous reinforcing material.
(2-4) The crystalline resin composition of Term (2-3) is preferably higher in fluidity than the crystalline resin composition with nigrosine (original nigrosine, generally hydrochloride) as a substitute for the nigrosine compound contained therein. For example, the crystalline resin composition of Term (2-3) preferably has a spiral flow length longer by not less than 10%, more preferably not less than 15%, and still more preferably not less than 20%, under conditions corresponding to the ordinary molding conditions for a crystalline resin composition containing a fibrous reinforcing material.
(2-5) The crystalline resin composition of Term (2), (2-1), (2-2), (2-3) or (2-4) may contain aniline black.
(2-6) The crystalline resin composition of Term (2), (2-1), (2-2), (2-3), (2-4) or (2-5) may contain carbon black.
(3) The fiber-reinforced crystalline resin molded product of the present invention comprises a fibrous reinforcing material and the nigrosine compound of Term (1), (1-1), (1-2), (1-3), (1-4), (1-5) or (1-6) contained resin, wherein the surface gloss is higher than that of the fiber-reinforced crystalline resin molded product with nigrosine as a substitute for said nigrosine compound.
The fiber-reinforced crystalline resin molded product of the present invention preferably higher by not less than 10% than the fiber-reinforced crystalline resin molded product containing nigrosine as a substitute for the nigrosine compound, in terms of gloss value as determined at an incidence angle of 60 degrees with respect to the test piece, using a glossmeter [produced by Suga Test Instruments, trade name: HG-268], for example.
(4) The method of the present invention for lowering the crystallization temperature of a crystalline resin is characterized in that the crystallization temperature of the crystalline resin is lowered by not less than 7xc2x0 C. from that of the original thermoplastic resin containing no nigrosine compound by containing the nigrosine compound of Term (1), (1-1), (1-2), (1-3), (1-4), (1-5) or (1-6) in the crystalline resin.
(5) The method of the present invention for improving the fluidity of a crystalline resin is characterized in that the fluidity of the crystalline resin is improved in comparison with that of the original thermoplastic resin containing no nigrosine compound by containing the nigrosine compound of Term (1), (1-1), (1-2), (1-3), (1-4), (1-5) or (1-6) in the crystalline resin.
This method for improving the fluidity of a crystalline resin may be such that a fibrous reinforcing material is contained in the crystalline resin.
(6) The method of the present invention for improving the surface gloss of a crystalline resin is characterized in that the surface gloss of the crystalline resin is improved in comparison with that of the original thermoplastic resin containing no nigrosine compound by containing the nigrosine compound of Term (1), (1-1), (1-2), (1-3), (1-4), (1-5) or (1) in the crystalline resin.
(6-1) The method of Term (6) for improving the surface gloss of a crystalline resin may be such that a fibrous reinforcing material is contained in the crystalline resin.
(7) A crystalline resin formulated with the nigrosine compound of the present invention is highly fluid while in a thermally molten state during molding, well spreads through all portions of the mold, and shows excellent dimensional stability during heating, thus enabling smooth molding treatment. For this reason, fine ruggedness is unlikely to occur in the surface of the molded product and the molding precision is good. This is quite advantageous in molding using large-sized molding machines, molding for precision molded products, and molding products undergoing rigorous requirements of dimensional precision. In addition, this is conspicuous in the case of crystalline resin compositions containing a fibrous reinforcing material, in which coloring agents and additives are considerably difficult to disperse, and the fluidity is reduced, because of the influence of the fibrous reinforcing material.
A crystalline resin formulated with the nigrosine compound of the present invention has a crystallization temperature lower that that of the original crystalline resin not containing said nigrosine compound. On the basis of this crystallization temperature reduction, the molding temperature for a crystalline resin composition can be set at low levels. For this reason, it is easily possible to reduce molding cost and suppress molding failure. In addition, because the shrinkage of the molded product upon cooling during molding is decreased, the molding precision improves so that the anisotropy of molded product strength can be well reduced, and a molded product with excellent surface gloss, appearance and dimensional stability during heating can be obtained. Regarding the obtainment of a molded product with excellent surface gloss and appearance, this effect is remarkable in the case of crystalline resin compositions containing a fibrous reinforcing material, which tend to have the fibrous reinforcing material floating on the surface of the molded product. Furthermore, as the crystallization temperature lowers, the allowance for adjustment of metal mold temperature and injection time in injection molding broadens so that the crystallization temperature of the molded product can be easily adjusted over a desired range. By optimally setting the metal mold temperature and injection time, the surface gloss of a molded product can be improved.
When the nigrosine compound of the present invention is formulated in a crystalline resin to color the crystalline resin, a uniformly and brilliantly colored molded product having a higher OD value than that obtained with conventional nigrosine (hydrochloride), and excellent surface gloss, is obtained; this effect is remarkable in the case of crystalline resins containing a fibrous reinforcing material, in which the fibrous reinforcing material is likely to float on the surface. Furthermore, the nigrosine compound of the present invention causes minimal fading and discoloration in the crystalline resin during pellet drying, formulation, kneading and molding before extrusion molding.
The nigrosine compound of the present invention surpasses nigrosine (hydrochloride) and black pigments which have traditionally been used for coloring crystalline resins in terms of dispersibility and/or compatibility for crystalline resins. With this feature, the nigrosine compound of the present invention is capable of more uniformly black coloring a crystalline resin with good appearance and surface shape or texture even when the dry color method is used. This uniform coloring effect is particularly remarkable in the case of coloring crystalline resins containing a fibrous reinforcing material, in which coloring agents are difficult to disperse due to the influence of the fibrous reinforcing material. Using in combination with carbon black, an inexpensive material of high light fastness, the nigrosine compound of the present invention makes it possible to achieve cost reduction and improved light fastness.
In addition, when the nigrosine compound of the present invention is formulated in a crystalline resin to color the crystalline resin, the solvent resistance is improved in comparison with conventional nigrosine (hydrochloride).
The nigrosine compound of the present invention is capable of brilliantly coloring a crystalline resin (fiber-reinforced or not).
The crystalline resin of the present invention, which is formulated with the nigrosine compound of the present invention, shows good fluidity while in a molten state during molding.
In addition, because the nigrosine compound of the present invention permits significant reduction in the contents of impurities likely to vaporize upon hot melting during molding and those reactive to crystalline resins, in comparison with conventional nigrosine (hydrochloride), crystalline resins formulated with the nigrosine compound of the present invention have effectively suppressed weight loss and gas generation during molding, and undergo minimal changes in the physical properties thereof. With these features, crystalline resins formulated with the nigrosine compound of the present invention are excellent in molding precision, and produce molded products having appearance-related properties, such as surface gloss, and surface shape or texture, improved well. The fiber-reinforced crystalline resin molded product of the present invention, in particular, has a good surface gloss.
According to the method of the present invention for lowering the crystallization temperature of a crystalline resin, the crystallization temperature of a crystalline resin composition can be lowered in comparison with that of the original thermoplastic resin containing no nigrosine compound.
According to the method of the present invention for improving the fluidity of a crystalline resin, the fluidity of a crystalline resin, including those containing a fibrous reinforcing material, can be improved in comparison with that of the original thermoplastic resin containing no nigrosine compound.
According to the method of the present invention for improving the surface gloss of a crystalline resin, the surface gloss of a crystalline resin, including those containing a fibrous reinforcing material, can be improved in comparison with the original thermoplastic resin containing no nigrosine compound.